Patent flour is the highest-quality grade of white wheat flour, made from the purest portion of the wheat kernel’s starchy interior (the endosperm) with virtually all bran and germ removed. It’s the standard white flour used across North American bakeries and food manufacturing, prized for its light color, low ash content, and consistent baking performance. The name dates back to 1870, when the U.S. Patent Office granted George T. Smith a patent for the milling equipment that first produced this refined grade at a mill near Minneapolis, Minnesota.
How Patent Flour Is Milled
All wheat flour milling works toward the same basic goal: separating the bran and germ from the endosperm, then grinding the endosperm into flour. What makes patent flour different is how aggressively it’s refined after that initial separation.
The process starts with the break system, which cracks open wheat kernels and scrapes the endosperm away from the bran coat. The resulting particles, called middlings, are a mix of clean endosperm chunks, bran fragments, and pieces where bran is still attached to endosperm. These get sorted by machines called plansifters (which separate by size) and purifiers (which use sieves and airflow to separate by size, density, and shape). The cleanest endosperm particles move on to the reduction system, where they’re ground into fine flour.
Patent flour comes from only the cleanest, most thoroughly purified streams in this process. The streams with more bran contamination get classified as lower grades. The result is a flour that’s whiter, finer, and more uniform than what you’d get if you simply ground all the endosperm together without sorting.
Grades of Patent Flour
Not all patent flour is the same. Mills divide it into sub-grades based on how much of the total flour output they include, with tighter selections producing purer (and more expensive) flour.
- Short patent (or top patent): The most refined streams only, representing roughly 50% of the total flour extracted. Ash content runs around 0.30% to 0.35%, meaning almost no bran particles made it through. This is the whitest, mildest flour a mill produces.
- Medium patent: A slightly broader selection that includes streams with an intermediate level of refinement.
- Long patent: Includes still more streams, with ash content in the 0.35% to 0.40% range. It captures more of the endosperm but accepts a bit more bran contamination in the process.
The term “extraction rate” describes what percentage of the wheat kernel ends up in the final flour. A lower extraction rate means more material was discarded, producing a purer product. Short patent flour has the lowest extraction rate of any commercial flour grade.
Patent Flour vs. Clear Flour vs. Straight Flour
Once the patent flour streams are pulled out, what remains is called clear flour. Despite its name, clear flour is actually darker, coarser, and stronger-tasting than patent flour because it contains more bran particles. It has higher protein (about 12.3% compared to patent’s 10.8%) and higher ash (0.60% vs. 0.39%), but that extra protein doesn’t translate to better baking performance. The gluten in clear flour is lower quality and doesn’t hold gas bubbles as well during fermentation. Clear flour is the least expensive commercial grade and finds its niche in rye breads and dark whole grain loaves where its grayish color blends in.
Straight flour is simply what you get when you combine all the patent and clear flour streams together without sorting them. It sits between the two in color, protein, and ash content (roughly 0.48% ash and 11.3% protein). Straight flour is popular in France, while North American bakers overwhelmingly prefer patent flour.
How It Performs in Baking
Patent flour’s reputation rests on what it does in dough. Stronger flours with high-quality gluten resist gas cell coalescence during fermentation, which is a technical way of saying the tiny bubbles in your dough stay small and evenly distributed instead of merging into big, irregular holes. The practical result is higher loaf volume, a finer and more uniform crumb, and bread that’s both stronger and more extensible when you pull it apart.
The low bran content matters too. Bran particles physically cut through gluten strands, weakening the dough’s structure. By stripping out nearly all the bran, patent flour lets gluten networks develop fully, giving bakers more control over texture. This is why it’s the default choice for sandwich breads, rolls, pastries, and any baked good where a white, even crumb and mild flavor are the goal.
Nutritional Trade-Offs
The same refining that gives patent flour its baking advantages strips away nutrients. The bran and germ contain most of the wheat kernel’s fiber, B vitamins, iron, and zinc. Patent flour retains very little of these.
To compensate, most countries require or encourage fortification. In the United States, enriched patent flour has thiamine, riboflavin, niacin, and folic acid added back, along with iron. These specific B vitamins are naturally present in unrefined wheat but lost during milling, so fortification is essentially restoring what the process removed. Some programs also add vitamin A and zinc, particularly in countries where deficiencies in those nutrients are a public health concern.
Even with enrichment, patent flour contains substantially less fiber than whole wheat flour. If the all-purpose flour in your pantry is labeled “enriched,” you’re almost certainly looking at a long or medium patent flour with vitamins added back in.
Where You’ll Find It
Most of the white flour sold in North America, whether labeled all-purpose, bread flour, or cake flour, starts as some grade of patent flour. The differences between those retail products come down to which wheat varieties were milled (hard wheat for bread flour, soft wheat for cake flour) and which patent grade was used. Cake flour, for instance, typically comes from short patent streams of soft wheat, giving it the lowest possible protein and ash for a tender, fine crumb. Bread flour uses patent streams from hard wheat, where the higher protein content builds the strong gluten network bread needs.
When a recipe simply calls for “flour” without further specification, it’s calling for patent flour. It’s so dominant in the North American market that it became the default, and every other type of flour is defined in relation to it.